Electric discharge device



Sept. 20, 1960 G. GALLET HAL ELECTRIC DISCHARGE DEVICE Filed July 17,1958 3 0 3 .h v m 2 M m nu. M HWWMWIWHIMHMMMMWWNWNMMMMMWW H r/ 7 /w 2 w2 INVENTORS I GEORGES GALLET, JEAN EDGAR PICQUENDAR,

THEIR ATTORNEY.

United States Patent() ELECTRIC DISCHARGE DEVICE Georges Gallet, LaCelle St-Cloud, and Jean Edgar Picquendar, Rueil Malmaison, France,assignors to Compagnie Francaise Thomson-Houston, Paris, France FiledJuly 17, 1958, Ser. No. 749,294

Claims priority, application France Aug. 1, 1957 11 Claims. (Cl.313-299) Our invention relates to electric discharge devices andpertains more particularly to ultra-high frequency devices.

As regards ultra-high frequency electric discharge devices, very highygain and short transit time of electrons between cooperating electrodesare generally considered highly desirable. However, in order to obtainhigh gain and to minimize electron transit time between electrodes it isgenerally necessary to minimize the spacing between electrodes such, forexample, as the spacing between the cathode and grid of the device. Insome devices this spacing is desirably very small and such smalldirnensioning has led the design of extremely small tubes with planarand parallel spaced electrodes. Included in such tubes have been planargrids comprising a plurality of spaced wire elements and it has beenfound that these Wire elements have a tendency at high temperatures texpand and undesirably contact the other electrodes. Various means havebeen employed for the purpose of -minimizing this undesirable tendency,including, for example, the pre-stressing of the grid wires. Fabricationof such elements have proved extremely complex, diliicult and costlywhile prevention of contact between the grid wires in other electrodeswas not assured.

Additionally, it is desirable in the presently considered types ofelectric discharge devices to increase power efficiency by increasingthe quantity of electrons which are effectively transmitted from anelectron emitter past a grid to a collector or anode. Heretofore, thishas been accomplished principally by controlling the size and spacing ofthe individual wires comprising the grid element, thus to increase theelectron permeability or transparency of the grid.

Still further, in the manufacture of ultra-high frequency devicesincluding closely spaced electrodes difliculties have been encounteredin connection with the undesirable effects of emission of both primaryand secondary electrons from grids and anodes.

Accordingly, the primary object of our invention is to provide a new andimproved ultra-high frequency electrie discharge device adapted for veryhigh gain and short transit time of electrons between cooperatingelectrodes.

Another object of our invention is to provide an electric dischargedevice including means for maximizing the quantity of electronstransmitted through a grid electrode from an emitter or to a collectorand improving the control of the device.

Another object of our invention is to provide a new and improved cathodestructure adapted for serving as a planar emitter and for emittingelectrons in a manner adapted for increased transmission of electronsthrough a grid and to a collector and so as to minimize secondaryemission from the grid and collector.

Another object of our invention is to provide a new and improved anodestructure adapted for serving efary emission therefrom.

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Further objects and advantages of our invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize our invention will be pointed out with particularity in theclaims annexed to and forming part of ths specification.

In carrying out the objects of our invention we provide electricdischarge device including an electrode assembly having a planarcathode, a planar grid, and a planar anode arranged in closely spacedparallel relationship. The cathode and anode are honeycomb-like instructure and include a plurality of longitudinally elongated Cells. Thegrid is also honeycomb-like in structure and includes a plurality oflongitudinally elongated passages. The cells in the cathode includeelectron emissive material only in the bottom portions thereof and thesurfaces in the bottoms of the cells in the anode are coplanar andcomprise the active anode surface of this electrode. The cellularstructures facilitate electrostatic focusing of electrons emanating fromthe cathode, passing through the grid and entering the anode. Ideallythe cells of the anode and cathode and the passages in the grid areaxially aligned. Magnetic iield means associated with the device alsoeffects magnetic focusing of the electrons.

For a better understanding of our invention reference may be had to theaccompanying drawing wherein:

Figure l is a schematic longitudinally sectionalized View of an electricdischarge device and associated magnetic field means constructed inaccordance with our invention;

Figure 2 is an enlarged fragmentary perspective view ofthe electrodeassembly of Figure l; and

Figure 3 is an enlarged fragmentary schematic illustration of theelectron beam flow between electrodes.

Referring to the drawing, there is illustrated in Figure l an ultra-highfrequency triode generally designated 1 and constructed in accordancewith our invention. From the outset it is to be understood that while wehave shown our invention as incorporated in a triode our invention isequally applicable to electric discharge devices including more thanthree electrodes.

The triode 1 includes a hermetically sealed envelope 2 which, forpurposes of illustration, can comprise a pair of ceramic wall sections 3and 4. Annular metal end wall sections 5 and 6 serve to close the endsof the envelope and as mounting means and electrical contacts for acathode and an anode assembly generally designated 7 and 8,respectively. A third annular metal member 9 is disposed between the`ceramic sections and serves to support a grid electrode 10 and formaking an electrical contact therewith. The ceramic sections 3 and 4 andthe metal members 5, 6, and 9 may be hermetically bonded by means of anynumber of ceramic-to-metal sealing techniques readily available in theprior art.

As also illustrated in Figure 2, the cathode assembly 8 can include ametal cup-like member 11 hermetically brazed adjacent the rim thereof tothe edge of an aperture centrally located in the end member 6. Thecuplike member 11 includes a planar bottom 12 and suitably brazedthereto is a planar honeycomb-like metal member 13, delining a pluralityof longitudinally elongated cells 14. In the embodiment illustrated, themember 13 can be advantageously formed of nickel. Also, While the member13 is illustrated and described as honeycomb-like, it is to beunderstood from the foregoing that the member 13 is cellular or isconstructed to provide a plurality of individual longitudinallyelongated cells and that it need not be honeycomb-like in the sense thatthe cells have any particular cross-sectional configuration.

Disposed in the bottoms only of each cell 14 and in spaced relation to aplane 15 defined by the outer edges of the cell y14 is a quantity ofelectron emissive material 16. The electron emissive material 16 isarranged in all cells so that the outer surface thereof defines a plane17, which plane is predeterminedly spaced inwardly of the cell edges orplane and is arranged parallel to the plane 15.

Disposed in the cathode member 1,1 and illustrated schematically inFigure 1 is a filamentary heater 18. When the heater 18 is energized asby the conduction therethrough of a suffcient current, the bottom 12 ofthe cup-like member 11 becomes heated which, in turn, heats the material16 to emissivity.

The electrons emanate from the cathode in a plurality of individualbundles or beams, as shown in Figure 3. This emanation of individualelectron beams is the result of the separation of the emissive areas bythe cellular or honeycomb-like construction of the member 13 and anelectrostatic focusing effect of the metal portions of the cell wallsbetween the planes 15 and 17. In a manner which will be described ingreater detail hereinafter this focusing effect increases thetransparency or electron permeability of the grid element 10 andminimizes secondary emission from the grid element and the electrodeassembly 7', Additionally, since it minimizes electron impingement uponthe edges and side walls of the passages of the grid 10, it minimizesundesirable heating thereof which, in turn, minimizes the coolingrequired and minimizes the emission of primary electrons therefrom.

Further, the honeycomb-like construction of the member 13 rigidizes itsuch that the member 13 will not be subject to any appreciable thermaldistortion even under extremely high filament temperatures. This enablesthe member 13 to be disposed extremely close to another element withoutdanger of contact thereof with such other element.

Cooperating with the cathode is the above-mentioned grid element 10. Thegrid element 10 comprises a honeycomb-like member also and is ofsufficient thickness that individual passages or openings 20` definedthereby are longitudinally elongated in relation with the widths of thecells. The passages 20 of the grid 410 also need not have any particularcross-sectional configuration. The grid can be copper and can beadvantageously formed by compressing a bundle of copper coated aluminumwires until the copper coatings of adjacent Wires become fused together,then slicing a disk of the proper thickness from the bundle andthereafter dissolving the aluminum from the disk with an appropriateagent so as to leave only the honeycomb-like copper grid. The passages20 preferably correspond in number to the cells 14 in the cathode andideally are axially aligned therewith. The honeycomb-like constructionof the grid rigidizes it also, and adapts it for being extremely closelyspaced to another electrode, such as the cathode, without danger ofcontact therebetween due to thermal distortion. Thus, the opposingsurfaces of the grid and other electrode on either side can be 4disposedextremely close and maintained substantially parallel and separated atsubstantially high operating temperatures. This enables a substantialreduction of the transit time of electrons between electrodes withoutdanger of undesirable contacting between electrodes.

Additionally, the electron passages 20 of the grid 10 adapt it forelectrostatically focusing the bundles or beams of electrons emanatingfrom the cathode. This focusing is also illustrated in Figure 2. Theaxial alignment of the cells 1'4 of the cathode and the passages 20 ofthe grid and the mentioned electrostatic focusing effect by theseelements on electrons passing therethrough adapt the assembly forgreater grid transparency or electronpermeability since substantiallyall the electrons emanating from the cathode will pass through thepassages 20 of the grid without any substantial interception ofelectrons by the grid, even when the latter is positive. With this typeof arrangement we have been able to obtain extremely high gridtransparencies such, for example as transparency. This increases thegain capabilities of the device and minimizes heating of the grid andboth primary and secondaryemission due to electron impingement on thegrid.

Included in the device on the side opposite the grid is a planar anodemember 21 which is suitably brazed to the inner end of an anode block 22included in the assembly 7 and brazed adjacent its outer end in anaperture in the member 5. The anode member 21 is also honeycomb-like inconstruction for defining a plurality of individual cells 23. As regardsthe anode member 21 the cells need only be longitudinally elongated andneed not have any particular cross-sectional configuration. Ideally thecells 23 correspond in number with the cells and passages of the cathodeand grid, respectively, and are axially aligned therewith. The activeanode surfaces of the anode comprise the bottoms 24 of the individualcells 23. These bottoms or active anode surfaces are coplanar in a planeindicated by 25 and are predeterminedly spaced from the outer edge ofthe cells or a plane indicated by the line 26 defined by the outer sideof the anode member 21. Additionally, the plane 25 and, therefore, theactive anode surfaces 24, are predeterminedly closely spaced from and inparallel relation with planes 27 and 28 defined by the correspondingsides of the grid 10.

The anode member 21 is dimensioned such that the cells 23 are longerthan the transverse dimension or diameter of the areas 24. Thus, thewalls of the cells 23 have an electron focusing effect on the individualbundles or beams of electrons received therein from the cathode andthrough the grid, as also seen in Figure 3. Additionally, thisrelatively deep disposition of the active anode areas 24 effectentrapment of secondary electrons tending to leave the anode. Further,the focusing effect of the elementary electrons by the grid just beforethe anode and by the portion of the anode cell walls between the planes25 and 26 have the desirable effect of minimizing electron impingementon the walls of the cells including the edges of the cells in the plane26. This has the resultant desired effect of minimizing secondaryemission and avoiding secondary emission in a region, such as betweenthe planes 26 and 27 or adjacent the grid 10. Thus, it will be seen fromthe foregoing that our present construction enables extremely closespacing between the grid and anode because of the relative remotespacing of the active anode surfaces 24 from the grid and the cellularor honeycomb-like construction of the grid and anode which minimizes anytendency toward secondary emission from the anode toward theinterelectrode spacing between the grid and anode.

We have found it possible to construct electric discharge devices withextremely close interelectrode spacings of orders not obtainable withprior art teachings. Additionally, we have found it possible to operatea device constructed according to our invention with a positive gridwhich enables the achievement of extremely short cathode-to-grid transittimes of the electrons and which, in turn, lead to extremely highfrequency for a given grid-to-cathode spacing.

We have also found it possible to increase the operating efciency of theabove-described device by placing it in a magnetic field with the fieldaligned axially with the cells and passages of the electrodes. This canbe accomplished, for example, by disposing the device longitudinally ina magnetic coil of the type schematically illustrated in Figure l. Whenthe coil 29 is energized as by means of a suitable source 30, theresultant magnetic field has the desirable effect of increasing thefocusing of the individual electron beams emanating from the cathodecells 14, thus to facilitate passage through the grid and into the cells23 of the anode for being co1- lected by the active anode surfaces 24with minimal electron impingement on the walls of the grid passages 20and the anode cells 23.

In the foregoing, we have Stated that ideally the cells of the grid andcathode and the passages of the grid correspond in number and areaxially aligned. It is to be understood that for some purposescorrespondence in number and laxial `alignment will not be necessary forsatisfactory operation. v

While we have shown and described a specific embodiment of our inventionwe do not desire our invention to be limited to the particular formshown and described, and we intend by the appended claims to cover allmodiiications within the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electrode structure comprising a planar cellular metal memberdefining a plurality of parallel individual cells, the bottom surfacesof said cells being coplanar and constituting the active electrodesurfaces of said structure, and said cells being longitudinallyelongated in a direction perpendicular .to said bottom cells and havinga longitudinal dimension greater than the transverse dimensions thereof.

2. An electrode structure according to claim l, Wherein magnetic meansdene a magnetic field extending lon-gitudinally through said individualcells and substantially perpendicular to each said bottom surfaces ofsaid cells.

3. An elect-rode assembly comprising a first electrode including aplanar cellular member comprising a plurality of parallel individualcells, the bottom surfaces of said cells being coplanar and constitutingthe active electrode surfaces of said structure, said cells beinglongitudinally elongated in a direction perpendicular to said bottomsurfaces and having a longitudinal dimension greater than the transversedimensions of said cells, a planar hollow cellular Second electrodedefining a plurality of electron passages longitudinally elongated in adirection perpendicular to the plane of said second electrode, `and saidfirst and second electrodes being in closely paced parallel relation.

4. An electrode-assembly according to claim 3, wherein magnetic meansdene a magnetic eld extending longitudinally through said individualcells and substantially perpendicular to .fthe plane of said iirst andsecond electrodes.

5. An electrode assembly comprising a planar grid, and a planarhoneycomb-like anode, said anode including a plurality of longitudinallyelongated individual cells, said cells having bottom surfacesconstituting the active surfaces of said anode, said cells having adepth dimension greater than the transverse dimension of said bottomsurfaces thereof, and said active anode surfaces being in coplanar andclosely spaced relation to said grid.

6. An anode structure comprising a planar honeycomb-like metal memberdening a plurality of individual cells longitudinally elongated in adirection perpendicular to the plane of said Structure, each of saidcells having a closed bottom, the closed bottoms of said cellsconstituting the active surfaces of said anode, and said active surfaceseach being smaller in diameter than the -depth dimension of said cells,whereby secondary electrons are entrapped in said cells and interceptionof electrons by the walls of said cells is minimized by an electrostaticfocusing effect of the longitudinally elongated walls of said cells.

7. An anode structure comprising a planar honeycomb-like metal memberdefining a plurality of individual cells longitudinally elongated in adirection perpendicular to the plane of said structure, the bottomsurfaces of said cells constituting active anode surfaces, said activeanode surfaces being smaller in diameter than the depth dimension ofsaid cells, whereby secondary electrons are entrapped in said cells andinterception of electrons by the walls of said cells is minimized by anelectrostatic focusing eifect of said walls, and means effecting amagnetic eldextending substantially perpendicular to said bottomsurfaces of said cells for assisting in rlocusing said electrons.

8. An electrode assembly comprising a planar honeycomb-like gridincluding a plurality of longitudinally elongated passages, a planarhoneycomb-like anode including a plurality of longitudinally elongatedindividual cells corresponding to and axially aligned with saidindividual passages of said grid, said cells of said anode having bottomsurfaces comprising the active anode surfaces, and said active anodesurfaces being coplanar and closely spaced relative to said grid.

9. A high frequency electric discharge device comprising an envelope, aplurality of mutually insulated electrode elements contained in saidenvelope, said electrode elements including a cathode comprising aplanar cellular metal member defining a plurality of longitudinallyelongated individual cells, and electron emissive material on only thebottom surfaces of said cells and spaced inwardly from the edgesthereof, whereby the walls of said cells are adapted forelectrostatically focusing electrons emanating from said electronemissive material, a planar hollow cellular grid in closely spacedparallel relation with said cathode, said grid defining a plurality oflongitudinally elongated electron passages, and a planar cellular anodein closely spaced and parallel relation to said grid defining aplurality of individual longitudinally elongated cells, said cells ofsaid anode having coplanar bottoms comprising the active anode surfacesand being smaller in diameter than the depth d-imension of said cells,whereby secondary electrons are entrapped in said anode and collectionof electrons on the walls of said anode cells is minimized byelectrostatic focusing.

10. A high frequency electric discharge device comprising an envelope, aplurality of mutually insulated electrode elements contained in saidenvelope, said electrode elements including a cathode comprising aplanar honeycomb-like metal member defining a plurality of mutuallyparallel longitudinally elongated individual cells extendingsubstantially perpendicular to the plane of said metal member, andelectron emissive material in only the bottoms of said cells and spacedinwardly from the edges thereof, whereby the walls of said cells areadapted for electrostatically focusing electrons emanating from saidelectron emissive material, a planar honeycomb-like grid in closelyspaced parallel relation with said honeycomb-like member of saidcathode, said grid defining a plurality of longitudinally elongatedelectron passages extending perpendicular to the plane of said grid andcorresponding to and axially aligned with said cells of said cathode,and a planar honeycomb-like anode in closely spaced and parallelrelation to said grid dening .a plurality of individual mutuallyparallel longitudinally elongated cells extending perpendicular to theplane of said anode and corresponding to and axially aligned with saidpassages in said grid, said cells of said anode having coplanar bottomscomprising the active anode surfaces and being smaller in diameter thanthe depth dimension of said cells, whereby secondary electrons areentrapped in said anode and collection of electrons on the walls of saidanode cells in minimized by electrostatic focusing.

ll. High frequency lapparatus including an electric discharge deviceconstructed according to claim 9 and magnetic means establishing amagnetic eld extending longitudinally through said cells and passages ofsaid electrode elements and substantially perpendicular to said bottomsof said cathode and lanode cells for magnetically focusing electronsemanating from said cells of said cathode land extending through saidpassages of said grid into said cells of said anode.

(References on following page) 7 References Cited in the file of thispatent 2,636,142 UNITED STATES PATENTS 25481307 2,018,362 Herold 001.22, 1935 2,058,878 Holst oct. 2,7, 1936 5 49,790 2,358,542 ThompsonSept. 19, 1944 952,893 2,410,054 Efemun oct. 29, 1946 995,370

8 Garner Apr. 21, 1953 Hickey May 29, 1956 FOREIGN PATENTS y NetherlandsJan. 15, 1941 France May 9, 1949 France Aug. 14, 1951

